Rate and Duration of Bone Union for Conservative Treatment in Pediatric Lumbar Spondylolysis

STUDY DESIGN: Retrospective case series. OBJECTIVE: To report the detailed bone fusion rates and duration of treatment in unilateral and bilateral cases of pediatric lumbar spondylolysis (LS). SUMMARY OF BACKGROUND DATA: Early diagnosis and optimal conservative management for LS are crucial for achieving bony healing without surgery. However, existing research on the conservative treatment of pediatric LS, particularly regarding bone union rates and treatment duration for each stage of bilateral spondylolysis, is limited. METHODS: We retrospectively analyzed 590 pediatric patients (522 boys and 68 girls) under 18 years of age diagnosed with LS and treated conservatively from 2015 to 2021. The diagnosis was based on computed tomography scans and magnetic resonance imaging findings, with stages classified as very early, early, progressive, or terminal. Patient background, sports history, level and stage of spondylolysis, presence of spina bifida occulta, bone union rate, duration of conservative treatment, and recurrence rate were retrospectively analyzed. RESULTS: The overall bone union rate was 81.9%, with a mean conservative treatment duration of 53.7 days. Unilateral LS cases showed decreased bone union rates with stage advancement (very early; 98.2%, early; 96.0%, progressive; 64.3%). Bilateral LS cases with progressive or terminal stage demonstrated low bone union rates (very early/very early; 100%, early/very early; 94.1%, progressive/very early; 66.7%, early/early; 82.9%, progressive/early; 32.3%, progressive/progressive; 23.7%, very early/terminal; 0%, early/terminal; 50.0%, progressive/terminal; 11.1%). The duration of conservative treatment extended as the stage of the main and contralateral lesions progressed, ranging from 39.1 days (very early/none) to 105 days (progressive/terminal). The recurrence rate after bone fusion was 16.6%, with no differences based on lesion stage. CONCLUSIONS: In this series of 590 patients, conservative treatment yielded high bone union rates for pediatric LS. However, union rates decreased with stage advancement, especially in bilateral cases. These findings provide valuable insights for prognosticating natural history and outcome regarding LS treatment, bone union, and return to activity.